This invention relates to displaying video images.
Each video image in a sequence of video images displayed on an interlaced display device consists of two fields of data: one field contains the even lines and the second field contains the odd lines of the video image. The difference between these two fields (polarities) is positional and temporal. In order to properly display the sequence of video images on the interlaced display device, e.g., in a simultaneous video capture and television (TV) output operation, the polarity of the video image should match the polarity of the display device. That is, the even lines of a video image should be sent to the display device when the display device is displaying an even lines field and the odd lines of the video image should be sent to the display device when the display device is displaying an odd lines field. Because the source of the sequence of video images and the display device can have independent timing, this field synchronization may not always exist. One way to achieve this synchronization is by genlocking the display device to the source of the video images using a genlocking device. The genlocking device enables the display device to lock onto and synchronize itself with the incoming sequence of video images.